The performance of conventional digital systems is limited by the transmission interconnection between integrated circuits. In such systems, a transmitter sends data onto a channel by setting a signal parameter of an output signal, such as current or voltage, to one of a plurality of discrete values during each of a succession of intervals referred to herein as data intervals. The data is in turn received by a receiver on the channel. The receiving IC device needs to be able to recognize the discrete values set by the transmitter in the data so it may be used in the receiving IC device.
The transmitted data typically experiences corruption as it propagates through the channel from the transmitter to the receiver. Such corruption can cause pre and post inter-symbol interference (ISI) and make it more difficult, or impossible, for some receivers to determine the value of the signal parameter during each individual data interval. The corruption which causes ISI may arise from frequency dependent attenuation in the signal path, reflections from impedance discontinuities in the signal path, or other factors. Typically, signal components at higher frequencies are attenuated to a greater degree than signal components at lower frequencies. These problems typically become more significant in high-performance systems where data is transmitted at a high data rate.
Equalization schemes may be used in high-performance communication links to compensate for all or part of the corruption imposed by the channel and thus maintain an acceptable error rate. For example, equalization may include processes for emphasizing or attenuating a selected frequency or frequencies of a signal, often to compensate for frequency-specific attenuation of the signal.
It would be desirable to implement receivers with equalization components in such systems in a manner that improves circuit design while effectively maintaining or improving data throughput.